NUMB facilitates autophagy initiation through targeting SCF^β-TrCP2 complex.

Area of Science:

• Cellular Biology
• Molecular Biology
• Autophagy Research

Background:

• SCF E3 ligases regulate autophagy by controlling protein stability.
• Tight control of SCF activity is essential for maintaining autophagic flux.

Purpose of the Study:

• To investigate the role of Numb protein in regulating autophagy.
• To elucidate the mechanism by which Numb influences DEPTOR protein levels and autophagy.
• To examine the role of Numb in renal fibrosis.

Main Methods:

• In vitro ubiquitination assays to assess DEPTOR ubiquitination by SCFβ-TrCP2.
• Co-immunoprecipitation to study protein interactions (Numb, β-TrCP2, SKP1).
• Numb overexpression and depletion studies in cell culture and a mouse model of renal fibrosis.

Main Results:

• Numb increases DEPTOR protein abundance, enhancing autophagy flux.
• Numb inhibits SCFβ-TrCP2-mediated DEPTOR ubiquitination by binding SKP1, disrupting the β-TrCP2-SKP1 interaction.
• Numb expression is upregulated in mouse renal fibrosis and human chronic kidney disease.
• Numb depletion in renal tubules reduces DEPTOR, attenuates autophagy, and protects against kidney fibrosis.

Conclusions:

• Numb acts as a novel regulator of SCFβ-TrCP2 activity, fine-tuning autophagy.
• Numb plays a protective role in renal fibrosis by modulating DEPTOR levels and autophagy.